Commonly, in machinery involving rotating elements, the rotating shafts are supported by anti-friction roller bearings. A common configuration is for a bearing race to be press-fitted or otherwise secured to the rotating shaft. This inner shaft race cooperates with a larger diameter race, which circumscribes the first. The two races sandwich roller bearing elements, such as bearing balls, or tapered bearing elements, between each other.
During normal operation of a machine, the machine heats up. Due to this heating, the elements of the machine expand and clearances between parts constrict. It is necessary to design the machin such that it does not bind at elevated operating temperatures as a result of this expansion. Therefore, at lower start-up temperatures, the clearances between elements of the roller bearing would be greater than at elevated operating temperatures. Thus, the rotating shaft is not constrained to the ultimate degree, and may cause excessive runout during the machine start-up. Consequently, the dimensions of the material being processed by this machine will suffer greatly by the bearing clearance deviation, resulting in the end product being off-specification. Thus, product manufactured during the start up and cool down phases of the machine is wasted. Also, if this installation were designed for a maximum elevated temperature, the clearance in the bearing, at a lower temperature, would also be objectionable, without this device.
In order to overcome this problem in the past, shims have been added to the machine set-up to set the clearance for each maximum operating temperature. Setting the shims wastes time and requires the expertise of an engineer to calculate the shim thickness required for each temperature range.
Another method has been used for adjusting the clearance between the inner and the outer bearing races. This method does not, however, provide for automatic adjustment of the race-to-race clearance during thermal expansion of the bearing during operation. In this method, a standard dual track internal collar is used in conjunction with a pair of sets of tapered rollers. The outer race is a specially formed dual track race, having an annular projection extending from one end. This annular projection forms a circumferential guide surface for a hydraulically actuated annular piston. The piston moves inside the projection. The piston pushes against the end faces of one set of tapered rollers on the end which faces away from the second set of rollers. Before the machine is started up, the piston pushes the tapered rollers to a predetermined location. Because the rollers and both the inner and outer races are tapered, moving the roller axially along the race changes the radial gap separation between the inner and outer races. This method establishes a precise pre-operation adjustment, but it does not provide for automatic adjustment to thermal expansion. Further, because the annular piston rubs against the moving rollers, it is likely that significant wear of the piston and the rollers would occur.
An additional general problem encountered is that as the parts of the roller bearing wear, a widening of clearances occurs, thus also destroying the tolerance of the product.
Thus, it is an object of our invention to provide an automatic method for adjusting the clearances within a roller bearing due to thermal variations during the operation of a device, and to changes due to wear, that does not require manually setting shims, or the expertise required to calculate shim size. It is a further object to provide such an automatically adjusting bearing device, that is inexpensive to make, uses predominantly standard parts and that does not undergo an unacceptable degree of wear.